A 6 GHz 68 mW BiCMOS phase-locked loop

The design of a 6 GHz fully monolithic phase-locked loop fabricated in a 1 μm, 20 GHz BiCMOS technology is described. The circuit incorporates a voltage-controlled oscillator that senses and combines the transitions in a ring oscillator to achieve a period equal to two ECL gate delays. A mixer topology is also used that exhibits full symmetry with respect to its inputs and operates with supply voltages as low as 1.5 V. Dissipating 60 mW from a 2 V supply, the circuit has a tracking range of 300 MHz, an rms jitter of 3.1 ps, and phase noise of -75 dBc/Hz at 1 kHz offset     

Performance of GaAs-AlGaAs V-grooved inner stripe quantum-well wirelasers with different current blocking configurations

GaAs-AlGaAs V-grooved inner stripe (VIS) quantum-well wire (QWW) lasers grown by metalorganic chemical vapor deposition with different current blocking configurations, n-blocking on p-substrate (VIPS), p-n-p-n blocking on n-substrate (VI(PN)_nS) and p-blocking on n-substrate (VINS) have been fabricated and characterized. The VIPS QWW lasers show the most stable characteristics with effective current confinement: one of the lasers shows fundamental transverse mode, lasing up to 5 mW/facet, typical threshold current of 39.9 mA at 818.5 mm, an external differential quantum efficiency of 24%/facet, and characteristic temperature of 92 K. The current tuning rate was almost linear at 0.031 mm/mA, and the temperature tuning rate was measured to be 0.14 nm/°C. Comparison of the light output versus current characteristics of the lasers with different current blocking configurations is presented here     

Pollutant dispersion over two-dimensional hilly terrain

Numerical prediction of the wind flow and pollutant dispersion over two-dimensional hilly terrain is presented. The wind tunnel experiments are conducted to validate the numerical results of the flow field. Measured mean velocity profiles, turbulence characteristics, and surface pressure distributions show good agreement with the numerical predictions. The hypothesis of Reynolds number independency for an atmospheric boundary layer flow over aerodynamically rough terrain is numerically confirmed. The linear theory provides generally good prediction of speed-up characteristics for gently sloped low hills. The effect of two-dimensional double hills on the dispersion of pollutants from continuously or temporally released line source of different emission heights and locations is also investigated. The ground-level concentrations are considerably reduced as emission heights are increased. The variances of ground-level concentration with respect to time from a temporally released source are strongly influenced by the flow separation.     

On measures of vulnerability of interconnection networks

With the advent of distributed and multiple processing systems, the study of interconnection networks has developed into a field of its own. In most cases, the performance measures used to characterize the reliability of such networks have been primitive.It is our purpose, in this brief paper, to survey the many available measures of the vulnerability of interconnection networks. The most widely known is classical connectivity; however, measures more recently introduced in the graph theory literature are probably a better practical metric of reliability. Our objective is to make these measures more widely known, and to spur the development of good algorithms to calculate them in practical instances.     

Analysis of color symbology from the perspective of cultural semiotics focused on Korean costume colors according to the cultural changes

The purpose of this study was to analyze the symbolization of colors as cultural codes, based on costume colors. In order to study the significance of colors in cultural changes, we carried out a quantitative analysis and interpreted it from the perspective of cultural semiotics. The range of this study was focused on Korean costume colors, over diverse diachronic stages of Korean culture. For this study 1535 color samples were collected, measured with a spectrophotometer, and analyzed quantitatively according their diachronic stages of origin. As a result, red, blue, and yellow were found to be the most frequently used colors during the Chosun Dynasty, a period based on Confucianism. These colors acted as cultural codes with cultural significance. During the Modern times pink, light blue, and black increased in frequency and represented the reception of western culture, the changing sex role of women in society, and utilitarianism. In these days, neutral colors and grayish tones of all colors are the most significant colors of high frequency. The use of such colors is closely related to industrialization, mechanization, functionalism, and the changes of women's sex roles in the societies. They are used as cultural codes, especially to emphasize a rational and masculine image rather than a feminine image. © 2006 Wiley Periodicals, Inc. Col Res Appl, 32, 71–79, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20290     

A micromachined electrochemical sensor for free chlorine monitoring in drinking water.

In this work, we designed, fabricated and tested a disposable, flow-through amperometric sensor for free chlorine determination in water. The sensor is based on the principle of an electrochemical cell. The substrate, as well as the top microfluidic layer, is made up of a polymer material. The advantages include; (a) disposability from low cost; (b) stable operation range from three-electrode design; (c) fluidic interconnections that provide on line testing capabilities; and (d) transparent substrate which provides for future integration of on-chip optics. The sensor showed a good response and linearity in the chlorine concentration ranging from 0.3 to 1.6 ppm, which applies to common chlorination process for drinking water purification.     

A linear minimum mean square error multiuser receiver inRayleigh-fading channels

We generalize the multiuser (CDMA spread spectrum) communication systems to the fading environments. We first extend Verdu's (1986) conventional optimum receiver to Rayleigh-fading environments and then evaluate its performance. Having no knowledge of the received power at the receiving end, we therefore need an estimator to efficiently estimate the received signal strength of each user in fading environments. A linear minimum mean square error (LMMSE) unbiased estimator is proposed to attain this goal. By using the minimum mean square error (MMSE) Bayesian estimation, we further propose the LMMSE bit estimator for efficient demodulation. Its performance is close to the optimum multiuser receiver but with a much simpler polynomial complexity. To further reduce the complexity, we extend the LMMSE estimator to the sequential LMMSE estimator. In sequential estimation, we do not need to implement the matched filter banks and to perform the matrix inversion when estimating. In addition, it converges after approximately 2k iterations, where k is the number of users. With this fast convergence property and the simple structure, the sequential LMMSE estimator provides an attractive alternative to the implementation of a multiuser system     

Phase transformation of calcia-alumina-magnesia fibres produced by inviscid melt spinning

CaO-Al₂O₃-MgO (CAM) ceramic fibre produced via inviscid melt spinning (IMS) was investigated for phase transformation. Differential thermal analysis (DTA) on the as-spun CAM fibre gave two transformation peaks, one for exothermic peak at around 927°C and the other for endothermic one at around 1100°C. In order to identify each phase transformation x-ray diffraction (XRD) analysis was performed on the CAM fibres heat-treated to each phase transformation completion temperature. The exothermic peak was determined to represent crystallization of remaining amorphous phase in the as-spun CAM fibre. The endothermic peak was determined to correspond to transformation of non-equilibrium CaO · Al₂O₃ phase to equilibrium 3CaO· 5Al₂O₃ phase.     

Pore‐free mold‐pattern‐transfer method for barrier ribs of HD PDPs

Abstract— Among various barrier‐rib manufacturing processes, the mold‐pattern‐transfer method has potential to reduce processing cost as well as the manufacture of high‐resolution pixels. In this study, the effects of major processing variables of the mold‐pattern‐transfer process on the formation of air‐trapped pores within barrier ribs were examined. The results indicated that with an optimum combination of the processing variables, barrier ribs without trapped defects can be produced, demonstrating the possibility of reducing the number of processing steps and costs of barrier ribs.